Consider the following sentence made up of three letter words. The words represent what will eventually be codons in a strand of mRNA: if the bases in the codons are in the correct sequence, the proper protein is made, just as if the letters are in the correct sequence, the sentence makes sense and isn't a bunch of jibberish.

The bad cat saw the big dog and ran and bit him


If another fragment of DNA (with the sequence inserted dna) were to insert itself into a point in the original strand, it is likely that an abnormal protein will be made (the sentence will no longer make sense):

The bad cat sai nse rte ddn awt heb igd oga ndr ana ndb ith im


"Spelling" isn't the only concern either. The syntax of the sentence must make sense as well. So just as inserting large pieces of DNA into a strand usually prevents a normal protein from being made, so will the deletion of large fragments of the original strand. Consider our example sentence again:

The bad and ran and bit him

Although this sentence is spelled correctly (ie, "in frame"), it makes no sense because it's missing the words in the middle. Likewise, such a deletion in DNA would lead to a protein missing many of its amino acids, and will most likely not be functional.


Now that we've discussed insertions and deletions, consider the effects of point mutations. Point mutations can do one of three things:

Contributed by Deanna Raineri